Some semiconductor devices contain a junction field effect transistor (JFET) having a top gate and a back gate to provide adequate control of the JFET channel resistance. The back gate may be provided by a buried layer having an opposite conductivity type from the JFET channel; the buried layer may be formed concurrently with other buried layers providing other functions in the semiconductor device, such as collectors for vertical bipolar junction transistors or isolation layers for high voltage transistors. Frequently, the depth of the buried layers is dictated by requirements of the vertical bipolar junction transistors or the isolation structures for the high voltage transistors, and is deeper than desired for optimum JFET performance, especially for a low voltage JFET.